This invention relates to axial split-pin tumbler-type lock mechanisms, particularly, to a lock mechanism designed to provide economy in manufacture.
In general, the axial split-pin tumbler-type lock mechanisms include a barrel assembly of a rotatable operating part and a stationary part, and the assembly is housed in a lock cylinder. Tumblers each including a driver element and a follower element are mounted in bores in the parts. The parts adjoin each other at an interfacial plane, the bores meet in alignment at the interfacial plane when the operating part is in a selected rotational position relative to the stationary part, and the tumblers are movable back and forth in the aligned bores. When the interfacial plane is bridged by one or more of the tumbler elements, the operating and stationary parts thereby are secured against rotation relative to each other. When the joints between the tumbler elements coincide with the interfacial plane, upon insertion of the proper key, the operating part may be rotated by means of the key, to accomplish a desired function. U.S. Pat. No. 3,102,412 is illustrative of the lock mechanisms.
The tumbler bores in the prior lock mechanisms of the foregoing type are enclosed within the bodies of the operating and stationary parts, and are formed by drilling solid bodies, or by molding and sintering metal powder. Drilling may result in certain defects or manufacturing disadvantages, caused by drill runout, drill vibration, and chip and burr formation. Additional reaming of the operating and stationary parts in pairs or sets is required, and the parts must be stocked and used in the resulting matched pairs. Elliptical holes may be formed, which decrease pick-resistance. Drill bits break, resulting in lost time. On the other hand, the sintered metal molding method of manufacture is more expensive than the drilling method.